1

INTRODUCTION TO NUTRITION AND PROTEINS

Santosh KIntern

2

NUTRITION

• Nutrition may be defined as a science of food and its relationship with health.

• Nutrients are specific dietary constituents such as proteins, carbohydrates, fats, vitamins and minerals.

• Dietics is the practical application of principles of nutrition: includes planning of meals for the well and the sick.

3

CHANGING CONCEPTS

• Nutrition is the corner stone of socio economic development.

• The concept that health sector alone is responsible for tackling the nutritional ills of the society has faded away.

• Broad inter- sectoral and integrated approach of sectors of development is needed to tackle today’s nutritional problems.

4

• Specific nutritional deficiency diseases have been indentified and technologies developed to control them.

• Importance of nutrition for immunity, fertility, maternal and child health and family health have gained importance.

• Role of dietary factors in the pathogenesis of non communicable diseases like CHD, diabetes and cancer have gained importance.

5

NUTRITIONAL EPIDEMIOLOGY :Epidemiological assessment of nutritional status of communities, nutritional and dietary surveys, nutritional surveillance, nutritional indicators and nutritional interventions-collectively called as nutritional epidemiology.

• Promotion of nutrition is one of the eight elements of primary health care.

6

CLASSIFICATION OF FOODS

BY ORIGIN:a)Animal originb)Vegetable origin

BY CHEMICAL COMPOSITION:a)Proteinsb)Carbohydratesc)Minerals d)Fatse)Vitamins

7

BY PREDOMINANT FUNCTIONS:a) Body building foods: eg. Milk ,meat, poultry, pulsesb) Energy giving foods: eg. Cereals, sugar, roots and tubers, oils and fatsc) Protective foods: eg. Vegetables, fruits, milk

BY NUTRITIVE VALUE:d) Cereals and milletse) Pulsesf) Vegetablesg) Nuts and oil seeds

8

BY NUTRITIVE VALUE:e) Fruitsf) Animal foodsg) Fats and oilsh) Sugar and jaggeryi) Condiments and spices

9

NUTRIENTS• Are organic and inorganic complexes contained in

food.

• They can be classified into 1.Macro nutrients2.Macro nutrients

10

MACRONUTRIENTS: • They are also called as proximate principles. • In Indian dietary, they contribute to the total

energy intake in the following proportions: proteins: 7-15% fats: 10-30% carbohydrates 65-80%

MICRONUTRIENTS: Vitamins and minerals.

11

PROTEINS

• The word protein by derivation means that it is of first importance.

• Proteins are complex organic nitrogenous compounds and composed of carbon, hydrogen , oxygen , nitrogen and sulphur in varying amounts.

• Proteins constitutes about 20 percent of the body weight in adults.

12

• Polypeptides are made by polymerization of amino acids through peptide bonds

• Big polypeptide chains containing more than 50 amino acids are called proteins.

13

PRIMARY STRUCTURE: determined by the sequence of amino acids

SECONDARY STRUCTURE: occurs when the amino acids are linked by hydrogen bonds.

TERTIARY STRUCTURE: formed when alpha helices and beta pleated sheets are held together by week interactions

QUARTERNARY STRUCTURE: consists of more than one polypeptide chains.

14

• Out of the 20 amino acids needed by the human body, 8 are essential because the body cannot synthesize them in amounts corresponding to the needs and hence must be obtained from dietary sources.

• Essential amino acids are- leucine, isoleucine, lysine, methionine, phenylalanine, threonine, valine, tryptophan and Histidine.

15

• A protein is said to be biologically complete if it contains all the amino acids in amounts corresponding to human needs.

• Animal proteins are superior to vegetable proteins as they are biologically complete.

16

ASSESSMENT OF PROTEIN• PROTEIN QUALITY: is assessed by comparison to a

reference protein(egg protein).

• There are two methods of assessment of protein quality:

a)Amino acid score b)Net protein utilization

17

• AMINO ACID SCORE:

Amino acid score=mg of amino acid per g of test protein ×100 mg of the same amino acid per gram

of reference protein Starches - 50-60 Animal foods – 70-80

18

• NET PROTEIN UTILIZATION(NPU) : It is the product of digestibility coefficient and biological value divided by 100.

NPU= Nitrogen retained in the body × 100 Nitrogen intake

• In calculating protein quality, 1 g of protein is assumed to be equivalent to 6.25g of nitrogen.

• Total protein requirements varies with the NPU of dietary proteins.NPU of Indian diet varies between 50 and 80.

19

• PROTEIN QUANTITY: one way of evaluating food as a source of protein is to determine what percent of their energy value is supplied by their protein .

protein energy ratio= energy from protein×100total energy in diet

It is recommended that protein should account for approximately 10-12 % of the total energy intake.

20

SOURCES OF PROTEINS

• Animal sources: Milk , meat, eggs, cheese, fish

• Vegetable sources: Pulses, cereals, beans, nuts,

oils and seeds. • In India cereals and pulses are the main

sources of proteins as they are cheap, easily available and consumed in bulk.

21

PROTEIN CONTENT OF FOODS

FOOD PROTEIN(g. per 100g.. Of food)

Milk 3.2 – 4.3Meat 18 – 26Egg 13Cereals 6 – 13 Pulses 21 – 28 Soyabean 43.2

22

PROTEIN REQUIREMENTS

• ICMR expert group suggested an intake of 1gram of protein per kg of body weight for adult males and females , assuming NPU of 65 for dietary proteins.

23

GROUP CATEGORY/AGE PROTEIN REQUIREMENT

MAN Sedentary workModerate workHeavy work

60g/d

WOMAN Non pregnant 55g/d

pregnant 78g/d

Lactating 0-6 m 74g/d

Lactating 6-12 m 68g/d

INFANTS 0-6 months 1.1g/kg/d

6-12 months 1.69g/kg/d

CHILDREN 1-3 years 16.7g/d

4-6 years 20.1g/d

7-9 years 29.6g/d

24

GROUP CATEGORY/AGE PROTEIN REQUIREMENT

BOYS 10 – 12 Years 39.9 g/d

GIRLS 10 – 12 Years 40.4 g/d

BOYS 13 – 15 Years 54.3 g/d

GIRLS 13 – 15 Years 51.9 g/d

BOYS 16 – 17 Years 61.5 g/d

GIRLS 16 – 17 Years 55.5 g/d

25

FUNCTIONS OF PROTEINS

A) Body building.B) Repair and maintenance of body tissues.C) Maintenance of osmotic pressure.D) Synthesis of substances like antibodies,

plasma proteins, hemoglobin, enzymes, hormones and coagulation factors.

26

PROTEINS CLASSIFIED BY FUNCTION

• CATALYTIC : Enzymes.

• STORAGE: Ovalbumen (in eggs), casein (in milk), zein (in maize).

• TRANSPORT: Haemoglobin.

• REGULATORY:Hormones (eg. insulin) and neurotransmitters.

27

• CONTRACTILE: Actin, myosin, dynein (in microtubules)

• PROTECTIVE: Immunoglobulin, fibrinogen, blood clotting factors

• STRUCTURAL: Cell membrane proteins, keratin (hair), collagen .

28

PROTEIN METABOLISM• Proteins are not stored in the human body.• They are constantly broken down into their

constituent amino acids and then reused for protein synthesis.

• The overall turnover in adult man is equivalent to replacement of 1-2% of the body protein each day.

• The amount of a specific protein in the body is kept constant.

29

DEFICIENCY DISEASES

• Protein deficiency occurs along with energy deficiency, hence called PROTEIN ENERGY MALNUTRITION.

• The current concept of PEM has two clinical forms- KWASHIORKOR and MARASMAS.

• They can be prevented by health promotion, good diet, immunisation, food fortification, early diagnosis and treatment and rehabilitation.

30

REFERENCES

• Park K . Textbook of Preventive and Social Medicine. 22nd ed. Banarasidas Bhanot publishers;2013: 563-565,588-589,592

• Vasudevan DM . Text book of biochemistry. 5th ed. Jaypee brothers medical publishers;2009:18,21,27,31- 32

• ICMR:recommended dietary allowances available from url( www.icmr.nic.in/final/RDA-2010.pdf ) accessed on 22/8/14 at 8:00PM.

31

THANK YOU